MacGREGOR new Roll-up-Roll mechanism for side-rolling hatch covers dramatically reduces the number of hydraulic cylinders required and also allows the correct rubber compression to be easily adjusted during service to compensate for wear

Side-rolling hatch covers from MacGREGOR with a new Roll-up-Roll mechanism offering higher operating efficiency and safety, with lower maintenance are specified for the debut newbuilding from China new Shanghai Waigaoqiao Shipbuilding (SWS) yard. Last year a 175,000 dwt bulk carrier was ordered by Hong Kong-based Tai Chong Cheang Steamship (TCC), which subsequently exercised an option for a sistership.

Each of the nine cargo holds will be equipped with a MacGREGOR side rolling-type hatch cover comprising twin panels stowing to each side. The covers will offer clear openings 15.47m long x 16.5m wide (Nos 1 and 9 holds) and 15.47m x 20m (Nos 2-8 holds).

Each panel will be operated by a hydraulic motor and rack-and-pinion system exploiting a new patented type of hydraulically-actuated self-locking Roll-up-Roll mechanism which is automatically secured when the covers are closed. The panels are raised together into the rolling position by this mechanism whose benefits in lifting and cleating are summarised as:

• self-locking automatic cleating
• only 18 hydraulic cylinders for the complete hatch cover shipset, yielding better performance and lower maintenance than from traditional wheel-lifting systems featuring 72 cylinders
• improved safety as there is no possibility of cleats being left unsecured
• increased cargo handling efficiency as no labour is required to open or close the cleats.

Adjustability is another important feature of the new Roll-up-Roll mechanism: adjusting the foundation point on deck achieves the correct rubber compression in the meeting joint. This is an advantage at the installation stage, and also during service as it is possible later to compensate for wear and still maintain compression.

Installing limit switches (an option) would make it possible to check directly from the bridge that all hatch covers are closed and secured.

Sealing between the hatch covers and coamings, and between the cover panels, will be secured with MacGREGOR FlexSeal rubber packing.

Due for completion in 2003, this represents the fourth series of bulk carriers commissioned by TCC with MacGREGOR side-rolling hatch cover sets. The earlier orders all placed at South Korean yards called for two 170,000 dwt ships from Halla (deliveries in 1998), three 170,000 dwt ships from Samho, formerly called Halla (deliveries in 2001) and a pair of 173,000 dwt ships from Daewoo (deliveries in 2000/2001).